表面疏水改性促进煤系黏土矿物沉降的机理及试验研究

Mechanism and experimental study of surface hydrophobic modification promoting settlement of coal measure clay minerals

针对选煤厂高泥化煤泥水难沉降的现状,以煤系黏土矿物为研究对象,探索了絮凝剂聚丙烯酰胺(PAM)分别与十二烷基三甲基溴化铵(DTAB)、十六烷基三甲基溴化铵(CTAB)配合使用后黏土矿物沉降规律,并通过聚团影像观测、XPS分析、润湿热和接触角测定及Zeta电位试验,半定量分析了PAM分别与DTAB、CTAB配合使用,促进黏土矿物沉降的作用机理。结果表明:DTAB和CTAB的添加能够促进黏土矿物颗粒生成大聚团,进而提高黏土矿物颗粒初始沉降速度,并大幅度降低上清液浊度,且CTAB作用效果优于DTAB作用效果;当CTAB用量为1800 g/t、PAM用量为80 g/t时,矿物质悬浮液沉降效果较好,对应矿物颗粒初始沉降速度为43.32 m/h,浊度值为76 NTU,沉淀物高度为19 mm,聚团直径最大约为2.6 mm;通过XPS及矿物表面润湿性测试,发现阳离子表面活性剂与矿物表面作用,活性剂带正电荷的亲水基朝向带负电荷的矿物颗粒表面,通过“电中和”作用降低矿物颗粒表面负电位,使矿物颗粒间静电斥力减小,同时,活性剂疏水基脱离矿物颗粒表面定向排列,罩盖矿物颗粒表面含氧基团而增加矿物颗粒表面含碳基团含量,使矿物颗粒表面的润湿热绝对值减小及接触角增加,改变了矿物颗粒表面疏水性,促进了矿物颗粒疏水聚团,从而使矿物颗粒更易聚集沉降;CTAB的烷基链较DTAB的烷基链更长,故CTAB对矿物颗粒表面疏水改性的能力更强,CTAB作用后黏土矿物的沉降效果更好。

In response to the current situation of difficulty in settling of coal slime with high-mud content in coal preparation plants,this study explored the settling behavior of coal series clay minerals using a combination of flocculant polyacrylamide(PAM)with dodecyltrimethylammonium bromide(DTAB)and hexadecyltrimethylammonium bromide(CTAB).The clay mineral settling mechanism was semi-quantitatively analyzed through various techniques such as agglomeration image observation,XPS analysis,measurement of wetting heat and contact angle,and Zeta potential testing.The results show that the addition of DTAB and CTAB can promote the clay mineral particles formation of large clay particle aggregates,thus increasing the clay mineral particles settling velocity and considerably reducing the supernatant turbidity.Besides,CTAB is found to be more effective than DTAB.When the dosage of CTAB is 1800 g/t,and the dosage of PAM is 80 g/t,the settling effect is better,with an initial settling velocity of clay mineral particles is 43.32 m/h,a turbidity value of 76 NTU,a sediment height of 19 mm,and the maximum aggregate diameter is about 2.6 mm.XPS and surface wettability test results show that cationic surfactants interact with the mineral surface,with hydrophilic groups facing towards the particle surface,reducing the negative surface potential of the particles through“electro-neutrality”effects,resulting in the reduction of the electrostatic repulsion between the mineral particles.Meanwhile,the active agent hydrophobic groups detach from the mineral particle surface,covering the oxygen-containing groups and increasing the content of carbon-containing groups on the mineral particles surface,thereby reducing the absolute value of the wetting heat on the mineral particle surface,increasing the contact angle,changing the surface hydrophobicity of the mineral,promoting the hydrophobic polymerization of the mineral particles,and facilitating their aggregation and settling.Compared with DTAB,CTAB has a longer alkyl chain and stronger ability to modify the mineral particles surface hydrophobicity of the mineral,resulting in a better settling effect for clay minerals.